Interpretive Summary: Ultraviolet (UV) radiation and heat can have detrimental effects on the color and mechanical properties of leather. We have been working on the development of a finishing process using environmentally friendly antioxidants that improve the UV and heat resistance of leather. A natural antioxidant—mixed tocopherols were added to the coatings of leather that had been tanned with an organic tannage without using chromium salts. Mixed tocopherols are abundantly available in nature and are produced from a renewable source such as soybeans. Following exposure to artificial sunlight, the treated samples were evaluated for colorfastness to access the degree of UV- and heat resistance. Observation showed that treatment with mixed tocopherols resulted in significant improvement in mechanical strength and color fading resistance against UV radiation and heat. The results of this research could lead to an increase in demand for domestic production of high quality, durable leather, thereby contributing to the viability of the domestic tanning industry.

Technical Abstract:
Most leather products are constantly exposed to outdoor environments, therefore UV and heat resistance are very important qualities, particularly for non-chrome-tanned (chrome-free) leather. In recent years, we have addressed this problem and focused on an environmentally friendly finishing process that will improve the UV and heat resistance of leather. Tocopherols are well-known antioxidants commonly used in the cosmetic and food industries. Tocopherols have been reported as potent free radical scavengers and highly protective agents for collagen fibers against UV and heat damage. Our previous research on alpha-tocopherol showed that it significantly improved UV and heat resistance of leather. Mixed tocopherols, on the other hand, are more abundant and are produced from a renewable source such as soybeans. We have investigated its potential to be applied to leather for improving UV and heat resistance. Experiments were conducted by adding 5 to 12% mixed tocopherols to the grain layer finishes of chrome-free leather. The treated samples were tested in a weatherometer, where they were exposed to artificial sunlight at a high temperature. Colorfastness and mechanical properties tests showed that mixed tocopherols significantly improved UV and heat resistance of leather.